This disclosure is generally directed to imaging members, and more specifically, the present disclosure is directed to single and multi-layered flexible, and rigid photoconductive imaging members with a hole blocking, or undercoat layer (UCL) comprised of, for example, a metal alkoxide, such as a conductive titanium alkoxide dispersed in a resin mixture of, for example, phenolic resin/phenolic resin blend or a phenolic resin/phenolic compound blend, and an epoxy resin binder or additive, and which layer can be deposited on a supporting substrate. More specifically, the present disclosure relates to layered photoconductive members containing an undercoat or blocking layer generated from a homogenous solution containing an epoxy resin, and wherein in embodiments the hole blocking layer is in contact with a supporting substrate, and which layer can be situated between the supporting substrate and the photogenerating layer, which is comprised, for example, of the photogenerating pigments of U.S. Pat. No. 5,482,811, the disclosure of which is totally incorporated herein by reference, especially Type V hydroxygallium phthalocyanine, and generally metal free phthalocyanines, metal phthalocyanines, perylenes, titanyl phthalocyanines, selenium, selenium alloys, azo pigments, squaraines, and the like. The imaging members of the present disclosure in embodiments exhibit excellent cyclic/environmental stability, and substantially no adverse changes in their performance over extended time periods since, for example, the imaging members comprise a mechanically robust and solvent resistant hole blocking layer, enabling the coating of a subsequent photogenerating layer thereon without structural damage; low and excellent Vlow, that is the surface potential of the imaging member subsequent to a certain light exposure, and which Vlow is about 20 to about 100 volts lower than, for example, a comparable hole blocking layer of a titanium oxide/phenol resin/silicon oxide dopant, and which blocking layer can be easily coated on the supporting substrate by various coating techniques of, for example, dip or slot-coating. The photoresponsive, or photoconductive imaging members can be negatively charged when the photogenerating layers are situated between the hole transport layer and the hole blocking layer deposited on the substrate.
In embodiments there is disclosed a photoconductor that includes a first layer (also referred to herein as “undercoat layer”) comprised of a polymer binder containing epoxy groups, and an ammonium titanate complex formed from the combination in the undercoat layer of a metal alkyl oxide and an amino siloxane. The present thick undercoat layer for xerographic photoreceptors can be coated at a thickness of, for example, up to about 25 microns. This permits rough substrates to be suitably coated and prevents or minimizes penetration of carbon fibers through the active layers to the substrate. The undercoat layer also provides improved hole blocking. Another important feature is the employment of the polymer binder containing epoxy groups, which polymer is crosslinkable with hydroxyl groups and/or amino groups upon heating, providing a robust undercoat layer. Exemplary polymers containing epoxy groups suitable for use include, but are not limited to, for example, EPON® 8111 (from Shell Chemicals Inc.), D.E.R® 330 and D.E.R® 663U (from Dow Plastics), and the like. When drying or coating, the epoxy resin will crosslink with amines and hydroxyl groups to form a robust undercoat layer, which will resist carbon fiber penetration and will be less sensitive to humidity.
Examples of epoxy resins which can be selected as the binder for the blocking or undercoat layer (UCL) include commercially available epoxy resins, such as the Epoxy resin EPON® 8111 as a cobinder with poly(vinyl butyral) wherein the EPON® can improve the interaction, especially the adhesion between the undercoat layer (UCL) and other layers present, such as the charge transport; and can also improve the coating quality of the UCL; cycle-up problems, and the like. Moreover, suitable further polymer, in addition to the epoxy resin, can be selected, which polymers are known, examples of which are provided herein.
Processes of imaging, especially xerographic imaging and printing, including digital, are also encompassed by the present disclosure. More specifically, the layered photoconductive imaging members of the present disclosure can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. The imaging members are in embodiments sensitive in the wavelength region of, for example, from about 500 to about 900 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the imaging members of this disclosure are useful in color xerographic applications, particularly high-speed color copying and printing processes.